Manufacture of copper oxide rectifiers



June 27, 1933. P. H. DOWLING MANUFACTURE OF COPPER OXIDE RECTIFIERS 7Filed Jan. 28, 1933 a 5 2 mm l V F mm 1115' ATTORNEY.

Patented June 27, 1933 UNITED STATES PATENT OFFICE PHILIP H. BOWLING, OFSWISSVALE, PENNSYLVANIA, ASSIGNOR TO THE UNION SWITCH & SIGNAL COMPANY,OF SWISSVALE, PENNSYLVANIA, A CORPORATION OF PENNSYLVANIA MLANUFAOTUREOF COPPER OXIDE RECTIFIERS Application filed January 28, 1933. SerialNo. 654,010.

My invention relates to copper oxide rectifiers, and has for an objectthe novel and improved method of manufacturing rectifiers of this type.j

I will describe several methods of manufacturing copper oxide rectifiersembodying my invention, and will then point out the novel featuresthereof in claims.

In the accompanying drawing, Fig. 1 is a diagrammatic view illustratingone step in a process embodying, my invention. Fig. 2 is a diagrammaticview illustrating the same step in a process embodying my invention, butwherein the breakdown discharge current does not pass through thejunction which is subsequently to be used as a rectifying junction. Fig.3 is a plan View, and Fig. 4 is a sectional view diagrammaticallyillustrating the step in the process embodying my invention wherewiththe passing of the breakdown discharge current through the junction,which is subsequently to be used for rectifying, is also avoided. Fig. 5is a diagrammatic view illustrating a method for preparing the rectifierfor the step in the process embodying my invention. In each of theseveral views similar reference characters designate similar parts.

In accordance with my invention, a copper disk is first treated to formcuprous oxide on both sides and the cupric oxide which appears on theouter surface of the cuprous oxide is then removed by any desired means.Referring to Fig. 1, the device then appears as indicated at R, where 2is the copper disk, and 3 and 3 are the layers of cuprous oxide on thetwo sides of the disk, respectively.

The reference characters 4 and 4* represent lead washers contacting withthe oxide layers 3 and 3, respectively.

5 is a source of direct current, which should be of from 200 to 300volts for the treatment of a rectifier consisting of a single quencheddisk, although this voltage range may be radically varied for differenttypes of rectifier disks. A condenser 6 may be connected either with thesource 5 or with the two lead washers 4 and 4" by means of a doublethrow double pole switch 7.

The method of operating the apparatus shown in Fig. 1 isas follows: Theswitch 7 1s first thrown downwardly to connect condenser 6 with thesource 5, thereby charging the condenser. The switch 7 is then reversed,so that the condenser discharges through the rectifier B. When thepolarity is as indicated in the drawing, the discharge current from thecondenser flows through the left-hand rectifying junction, that is, thejunction between the disk 2 and the oxide layer 3, in the highresistance direction, and the voltage is such as to break down thisjunction at one or more points, as indicated at 8. This dischargecurrent flows through the right-hand junction, that is, the junctionbetween disk 2 and oxide layer 3, in the low resistance direction,leaving this junction unharmed.

For the breakdown of a quenched rectifier disk 1% inches in diameter,the condenser 6 may be of the order of to 100 microfarads, although thisrange of capacities may be radically changed to meet the requirements ofthe specific disks under treatment. I have found that the conductingpath formed by the breakdown of the rectifier junction has arialsistance of approximately 0.0006 of an o m.

Referring to Fig. 2, the metal washer 4 is omitted and contact is madedirectly with the copper disk 2 as indicated at 19 in any convenientmanner. This direct connection with the copper disk makes it unnecessaryto pass the breakdown discharge current through the junction between thecopper disk 2 and the oxide layer 3, which junction is subsequently tobe used for rectifying. The process of chargingthe condenser 6 from thecurrent source 5 and then reversing the, switch 7 to discharge thecondenser 6 through the contact washer 4, oxide layer 3 and cop per disk2 to break down the oxide layer on that side of the disk at one or morepoints as indicated at 8 is similar to that described,

have not found, however, that any particular advantage is obtained bybreaking down the junction in the low resistance direction. In

either case the voltage is such as to break down the unction between thedisk 2 and the oxide layer 3 at one or more points as indicated by thereference character 8.

Another method to avoid passing the breakdown discharge current throughthe junction of the copper disk 2 and the'oxide layer 3, which 'un ctionis subsequently to be used for rectifying, is shown in Figs. 3 and 4. Inthis form, three washers 4", 10 and-11 are used for contacting with thedisk 2 on the side next to the junction to be broken down, the leadwasher 4", which is to form the connection in the final rectifier,covers substantially the full area of the insulating washer 11 on theoutside of that washer, and covers something less than one-half of thearea on the side next to the oxide layer 3; while, the metal washer 10covers something a little less than onehalf of the area of theinsulating washer 11 on the side next to the oxide layer 3. A tab 12connects the two portions of washer 4", and a tab 13 is formed on thewasher 10. These tabs 12 and 13 provide terminals for applying thebreakdown discharge current to the two metal washers 4 and 10. Thepolarity of the. breakdown discharge current is immaterial, but abreakdown of the oxide layer 3 must occur under the washer 4 asillustrated at 8 in Fig. 4. In this instance the-path for the breakdowndischarge current from the condenser 6 when the switch 7 is closed, is

from one terminal of the condenser 6 through tab 12, metal washer 4",through oxide layer 3 into the copper disk 2, the copper disk 2 backthrough the oxide layer 3 to the metal washer 10, tab 13 and to theopposite terminal of the condenser 6, or vice versa, depending upon thepolarity. In connection with this arrangement it is to be noted thatwashers 4" and 10 are s aced with their adjacent edges 19 and 20 atenough apart so that the path through the copper disk 2 is thepreferential path for the breakdown discharge current rather thandirectly through the oxide layer 3.

I have found that in electrically breaking down the junction between theoxide layer 3 and the copper disk 2 in the rocess embodying my.invention, it is pre erable that the layer.

the breakdown shall occur in the interior of the oxide layer rather thannear the edge of The location of the breakdown may be established inthemanner illustrated in Fig. 5. Contact is made on the oxide layer at twopoints ,14 and 15 and these points 14 and'15 are momentarily connectedto a source of relatively high voltage such for example as the secondarywinding 16 of a transformer T, the primary winding 17- of which isconnected to the convenient souroeof alternating current not shown. Animpedance 18 is connected in the circuit to limit the current fiow.- Adirect current source of relatively high potential may used in the placeof the transformer T if it seems desirable. I

have found that 3000- volts of alternating current, and a seriesimpedance of 12000 ohms will give satisfactory results. After such ainbefore always results in the junction between the oxide layer 3 andthe disk 2 breaking down in the locality of the points 14 and 15. The3000 volt current leaves no visible evidence of its passage and does notcompletely break down the junction. It appears simply to weaken thejunction locally so that the subsequent application of the breakdowndischarge current from the condenser will break ing down may be{accomplished after the rectifiier has been assembled. In the former caseit may be desirable to provide additional means for causing adhesionbetween the lead washer and the disk beyond thatwhich is furnished bythe sputtering of the lead into the break; this may be accomplished byproviding small quantities of glue or wax between the leadwasher and thedisk, which material will be warmed during the breakdown process and sowhen subsequently k cooled will assist in holding the lead washeragainst the oxide surface.

One advantage of a process embodying my invention is that the disksremain flatthroughout the entire process of production, and anotheradvantage is that when the disks are finished, they are uniform as tothickness. Still another advantage is that a low resistance contact isobtained. with the lead washer and the copper disk. It is 'also believedthat the aging of the finished rectifier is improved.

Although I have herein shown and described only certain methods for theprocess of manufacturing rectifiers embodying my invention, it "isunderstood that various changes and-modifications may be made there inwithin the scope of the appended claims without departing from thespirit and scope of my invention.

Having thus described my invention, what I claim is: i

1. The method of manufacturing a'copper neieeec oxide rectifier whichconsists in forming cuprous oxide on both sides of a copper disk,

.and electrically breaking down the rectifyance direction, leaving therectifying junc tion on the other side of the disk unharmed. 3. Themethod of manufacturing a copper oxide rectifier which consists informing cuprous oxide on both sides of a copper disk, and breaking downthe rectifying junction on only one side of said disk by passing currenttherethroug'h in the high resistance direction. I 4. The method ofmanufacturing a copper oxide rectifier which consists in forming cuprousoxide on both sides of a copper disk, and then applying across one ofthe oxide surfaces and the copper disk a difierence of electricalpotential of sufiicient value to electrically break down the rectifyinjunction on the one side of the copper disi, leaving 'the rectifyingjunction on the other side unmolested.

5. The method of manufacturing a copper oxide rectifier which consistsin forming cuprous oxide on both sides of a copper disk,

placing two inetal contacting washers on one side each covering only aportion of the cuprous oxide layer, and then applying across the twometal contacting washers a diderence of electrical potential ofsufiicient value to electrically break down the rectifying junctionbetween at least one of said washers and the copper disk, leaving therectifying junction on the other side of the copper disk unmolested.

6. The method of manufacturing a copper oxide rectifier which consistsin forming cuprous oxide on both sides of a copper disk, momentarilypassing current between two spaced points on one side of the disk toweaken the junction locally at said two ayer on said one side and thecopper disk a difference of electrical potential of suficient value toelectrically break down the rectify ing junction locally weakened atsaid two points, leavin the rectifying junction on the other side of t edisk unmolested;

7. The method of manufacturing a copper oxide rectifier which consistsin forming cuprous oxide on both sides of a copper disk, placing a metalcontacting washer on one side of the disk, and then applying across themetal washer and said disk a diiierence of electrical potential ofsufiicient value to electrically break down the rectifying junction onthat side ofthe disk to form a low resistance path for current in eitherdirection between the contacting washer and the disk. In testimonywhereof I afiix my signature.

PHILIP H. DOWLING.

oints, and then applying across the oxide

